The present invention relates to a seat belt device that is mounted on a vehicle, such as an automobile, for the purpose of protecting an occupant. More particularly, the present invention relates to a seat belt retractor locking the reel shaft from rotating to prevent the webbing from being pulled out when an emergency situation occurs.
As disclosed in the specification and drawings of U.S. Pat. No. 4,796,918, a typical conventional seat belt retractor mounted on a vehicle such as an automobile has a reel shaft for winding up a webbing, a frame for rotatably supporting both ends of the reel shaft, locking means disposed between the frame and the reel shaft for allowing the reel shaft to rotate normally and for preventing the reel shaft from rotating at least in a webbing unwinding direction at a time when it is necessary to prevent the reel shaft from rotating, deceleration sensing means which works when deceleration exceeding a predetermined value acts on the vehicle, and activating locking means for activating the locking means in accordance with the working of the deceleration sensing means.
In the seat belt retractor as mentioned above, since the reel shaft is usually free to rotate, the webbing is freely pulled out and the occupant can move forward. When an emergency situation occurs, for example, when a large degree of deceleration acts on the vehicle, since the deceleration sensing means senses the deceleration and operates, the locking means operates by the activating locking means. Since the operation of the locking means locks the reel shaft from rotating, the webbing is prevented from being pulled out so that the occupant is restrained by the webbing to prevent the inertial forward movement of the occupant.
In a typical conventional seat belt retractor as mentioned above, as shown in FIG. 22, a frame 102 for rotatably supporting both ends of a reel shaft 101 is formed in a U-shape by a press working and through-holes 102c and 102d are provided in a right-hand side wall 102a and a left-hand side wall 102b of the frame 102, respectively, so that the reel shaft 101 passes through the through-holes 102c and 102d. In this case, a webbing winding portion 101a of the reel shaft 101 is positioned between the right-hand side wall 102a and the left-hand side wall 102b. A right end 101b and a left end 101c of the reel shaft 101 pass through the through-holes 102c and 102d to protrude outside the right-hand and left-hand side walls, respectively.
Webbing flanges 101d, 101e are provided for winding or unwinding the webbing to the webbing winding portion 101a of the reel shaft 101 smoothly. Circular flanges 101f and 101g each having a diameter larger than the diameter of the through-holes 102c and 102d are provided to the inner surfaces of the webbing flanges 101d and 101g to prevent the reel shaft 101 from coming off the right-hand and left-hand side walls 102a and 102b.
However, as the circular flanges 101f, 101g as mentioned above are provided, the webbing winding portion 101a of the reel shaft 101 cannot pass through the through-holes 102c and 102d of the right-hand and left-hand side walls 102a and 102b of the frame 102 formed in the U-shape when inserting the reel shaft 101 into the frame 102 to dispose the webbing winding portion 101a between the right-hand side wall 102a and the left-hand side wall 102b. Therefore, as shown in FIG. 23, conventionally, the right-hand and left-hand side walls of the frame 102 are previously processed by bending to be in a shape that the distance between the right-hand and left-hand side walls becomes larger toward their ends. After the webbing winding portion 101a is disposed between the right-hand and left-hand side walls 102a and 102b and the right and left circular flanges 101f and 101g are disposed facing to the through holes 102c and 102d, the right-hand and left-hand side walls of the frame 102 are then processed by bending to be in the U-shape so that the reel shaft is assembled into the frame 102.
However, according to the conventional way of assembling the reel shaft 101 into the frame 102 as mentioned above, the reel shaft 101 must be retained in a predetermined position of the frame previously bent in the shape that the distance between the right-hand and left-hand side walls becomes larger toward their ends, and then the right-hand and left-hand side walls must be further bent in the U-shape by a press working. Therefore, it consumes not only plenty of labor but also many steps.